Question

A stopwatch is used to time a runner in a race. The diagrams show the stopwatch at the start and the end of the race. How long did the runner take to run the race?

A. $70:00{\text{sec}}$
B. $110:00{\text{sec}}$
C. $115:00{\text{sec}}$
D. $155:00{\text{sec}}$

Answer 1

This is a very simple question where we just need to carefully read the stopwatch time and subtract the start time from the time and we will get the total time taken by the runner to run the race.

Complete step by step answer:
Start time: $0:45:20$ which means ${\text{45min}}$ and $20{\text{sec}}$.
End time: $1:55:20$ which means $1{\text{h}}$, $55{\text{min}}$ and $20{\text{sec}}$
Now to calculate the time taken by the runner to run the race, we have to subtract the start time from the end time.
1{\text{h}}:55\min :20\sec - 0:45\min :20\sec \\\
$\Rightarrow 1{\text{h:10min}}$
We know that one hour consists of sixty minutes therefore the time required for the run to complete the race is $70\sec$.

Hence, option A is correct.

Additional information: A stopwatch is a handy timepiece designed to record the period which elapses between its activation and deactivation. In a manual stopwatch, the watch is started and stopped by a user pressing the button on it. However, in automatic timing, both starting and stopping are stimulated automatically, by sensors.

A mechanical stopwatch is powered by a mainspring that should be wound up by turning the knurled knob located at the top of the stopwatch. A big digital version of a stopwatch is created for viewing from a distance that can often be seen in stadiums and stations. These are more accurate timepieces than mechanical ones because of their crystal oscillator timing element.

Note: The least count of stopwatches are negligible. The less the least count more is the precision. Reading of the stopwatches should be read carefully in terms of hours and seconds. Keep the basic rule subtraction that only alike quantities be subtracted in mind when solving this problem.